Prior parking meters are known which increase revenues by detecting the presence or absence of a vehicle. U.S. Pat. No. 4,823,928 which issued to POM Incorporated in 1989, describes an electronic parking meter system that resets the timing circuit to zero when a vehicle is no longer detected in the associated parking space. The POM Incorporated parking meter is placed in an operational mode when a coin is deposited. When placed in the operational mode, a sonar range finder is turned on which detects the presence or absence of a vehicle in the associated parking space. The sonar range finder provides a signal to a microprocessor controller when the vehicle is no longer in the associated parking space, and the microprocessor controller resets the timer.
While the POM Incorporated parking meter assists in maximizing parking meter revenues, it does not catch parking meter violations. In order to catch parking meter violations, parking meter attendants and parking by-law enforcement officers patrol the streets. Typically, comparatively few enforcement officers are charged with responsibility for a huge number of parking meters, so enforcement is random, at best. This problem was addressed in the U.S. Pat. No. 5,777,951 which discloses a parking meter system in which a camera is used to record and store the image of the license plate of a parking violator. The parking meter includes a microcontroller and a timer coupled with the microcontroller. Payment acceptance means is coupled with the microcontroller for accepting payment for use of an associated parking space. The microcontroller initiates the timer for a prepaid parking interval upon receiving a signal from the payment acceptance means. Vehicle detection means is coupled with the microcontroller for detecting the presence or absence of a vehicle in the associated parking space. A communications modem is coupled with the microcontroller. The microcontroller initiates a call notifying authorities as to a parking violation upon the vehicle detection means signalling to the microcontroller the presence of a vehicle in the associated parking space after the expiration of the prepaid parking interval, or the microprocessor initiates the camera to take an image of a vehicle upon the vehicle detection means signalling to the microprocessor the presence of the vehicle in the associated parking space after the timer has signalled to the microprocessor the expiration of the prepaid parking interval. However in some instances, an experienced parking violator can prevent detection by obscuring the license plate with a covering, tape etc. There is therefore a need for a vehicle identification means for use with prior parking meter systems which is less vulnerable to circumvention.